The Bluefin-21, operated by the US Navy off the Australian vessel Ocean Shield, is an autonomous underwater vehicle (AUV) that can identify objects by creating a sonar map of the sea floor.

So far the submarine has completed nine missions, JACC says. Over the past week, it has scanned 80% of the circular search area with a 10km (six miles) radius with "no contacts of interest".

The centre said the submarine search would continue and discussions were taking place on its future focus. The submersible drone was seen by experts as the best chance of finding the plane's flight recorders

The Bluefin is operating at a depth of more than 4,000m (13,000 feet) but search teams may have to turn to other types of underwater vehicle capable of going deeper if it fails to find anything.

The daily operation involving some two dozen nations is already shaping up to be the most expensive in aviation history.

Authorities still do not know why the plane flew so far off course and finding the plane's flight recorders is seen as key to understanding what happened.

Using satellite data, officials have concluded that MH370 ended its journey in the southern Indian Ocean west of the Australian city of Perth.